Genes & Cells

Life’s essentials
Most of the DNA in the bacterium Caulobacter crescentus really isn’t necessary. Researchers used genetic tricks to map out the pages of the bacterium’s genetic instruction book that are essential to life in the lab. Of Caulobacter’s 3,876 genes, only 480 are essential, Stanford microbiologist Lucy Shapiro  and her colleagues report online August 30 in Molecular Systems Biology. Also necessary are 402 pieces of DNA that govern activity of genes and 130 pieces of DNA that don’t encode proteins. Of the 130 “non-coding” bits, “90 don’t fit any of the categories we know about, and we don’t have a clue what they do,” Shapiro says. —Tina Hesman Saey

Black Death bacterium is extinct
Fear not. A version of the plague bacterium that wiped out at least 30 percent of Europe’s population between 1347 and 1351 is a goner. Scientists have debated whether the plague bacterium Yersinia pestis really caused the Black Death because that plague had different symptoms than modern outbreaks of bubonic or pneumonic plague. Now scientists from the University of Tübingen in Germany and McMaster University in Canada and colleagues have found traces of Y. pestis in skeletons of Black Death victims. The team reports online August 29 in the Proceedings of the National Academy of Sciences that the Black Death bacterium was genetically different from modern plague strains and probably no longer exists. —Tina Hesman Saey

Yellow eyes get less sleep
Elderly people’s sleeping problems may be due to a natural yellowing of the eyes with age, a new study suggests. Researchers at the University of Copenhagen examined 970 Danish people between 30 and 60 years old. The team found that as people age, the lenses of their eyes yellow slightly, blocking out blue light wavelengths that help synchronize the body’s daily rhythms. The less blue light that got through to the retina, the more likely people were to have sleep disturbances, the researchers report in the Sept. 1 Sleep. Yellowing is sped up in smokers and people with diabetes and heart disease. —Tina Hesman Saey

Ancient antibiotic resistance
People have been fighting bacteria with antibiotics for more than 70 years, but a new study finds that the microbes have had at least a 30,000-year head start on building resistance. The finding, published online August 31 in Nature, contradicts the idea that resistance to antibiotics is a modern phenomenon brought about by misusing the drugs. Researchers at McMaster University in Hamilton, Canada, and colleagues isolated ancient DNA about 30,000 years old from the permafrost near Dawson City, Canada, and found genes for proteins that work together to inactivate the antibiotic vancomycin. Resistance to that antibiotic was previously thought to have first arisen in the late 1980s. —Tina Hesman Saey